Phyto

Principles and Resources for Site Remediation and Landscape Design

Kate Kennen, Niall Kirkwood

• Publisher: Routledge
• Year: 2015
• ISBN:
  9781317599005
• Edition: 1
• Topic: Architecture
• Subtopic: Urban Planning & Landscaping

Winner of the 2017 CBHL Literature Award of Excellence in Landscape Design and Architecture

Phyto presents the concepts of phytoremediation and phytotechnology in one comprehensive guide, illustrating when plants can be considered for the uptake, removal or mitigation of on-site pollutants. Current scientific case studies are covered, highlighting the advantages and limitations of plant-based cleanup. Typical contaminant groups found in the built environment are explained, and plant lists for mitigation of specific contaminants are included where applicable.

This is the first book to address the benefits of phytotechnologies from a design point of view, taking complex scientific terms and translating the research into an easy-to-understand reference book for those involved in creating planting solutions. Typically, phytotechnology planting techniques are currently employed post-site contamination to help clean up already contaminated soil by taking advantage of the positive effects that plants can have upon harmful toxins and chemicals. This book presents a new concept to create projective planting designs with preventative phytotechnology abilities, 'phytobuffering' where future pollution may be expected for particular site programs.

Filled with tables, photographs and detailed drawings, Kennen and Kirkwood's text guides the reader through the process of selecting plants for their aesthetic and environmental qualities, combined with their contaminant-removal benefits.

1: Phytotechnology and the contemporary environment: an overview

In this chapter, the key background issues and design topics surrounding plant-based remediation are introduced and an overview of the potential use of phytotechnologies in site design work is given. Chapter 1 also includes the current definition of the term phytotechnologies, and outlines the opportunities and constraints of vegetation-based remediation. Previous and current research on the subject is described and an outline of the legal framework in which phytotechnologies are used is provided. Finally, potential innovative applications are summarized as well as projected areas of future scientific and field research.

I	What is phytotechnology?

The authors have proposed a broader definition of phytotechnology than is currently available, so as to engage and integrate this work with contemporary site design practices:

Phytotechnology is the use of vegetation to remediate, contain or prevent contaminants in soils, sediments and groundwater, and/or add nutrients, porosity and organic matter. It is also a set of planning, engineering and design tools and cultural practices that can assist landscape architects, site designers, engineers and environmental planners in working on current and future individual sites, the urban fabric and regional landscapes.

Definition by Kirkwood and Kennen as an expansion of previous definitions (Rock, 2000; ITRC, 2009)

The major focus of phytotechnology in this book is on the plant-based remediation of soils and groundwater. Planted systems for stormwater and wastewater treatment are already commonly integrated in landscape design practice, therefore the book will only briefly address these topics. This work will also touch on air pollution as it relates to the natural ability of plants to bioaccumulate or degrade airborne pollutants or render them less harmful. Phytotechnology implements on-site scientific and engineering solutions to contaminants found predominantly in soils and groundwater, via introduced vegetation that is targeted to be self-sustaining and integrated in the site design.

Figure 1.1 Phytotechnologies

Following the above definition, the background to the term phytotechnology, and in particular its evolution over recent years, is worth describing. Confusion can result from a slight difference between the terms ‘phytoremediation,’ which is more traditionally used in scientific papers, and ‘phytotechnology,’ which is seen more in recent literature. Instances are not uncommon where the two terms have been used interchangeably, leading to further confusion about the subject.

II	The difference between phytotechnologies and phytoremediation

The term phytoremediation, or remediation by plants, simply describes the degradation and/or removal of a particular contaminant on a polluted site by a specific plant or group of plants. However, in addition to the degradation and/or removal of contaminants, phytotechnology also includes techniques such as the stabilization of pollutants within the surrounding soil or root structure of a plant and the preemptive installation of plant-based approaches so as to treat a pollutant or mitigate an ecological problem before it actually occurs. Stabilization utilizing plants does not actually remediate or break down the pollutants but renders them immobile in the soil, thus allowing no further contact to take place between the occupants of the site and subsurface contamination. In addition, the term phytotechnology may also include prophylactic advance plantings on a site that can help prevent contamination that could arise in the future from site activities. Where phytoremediation is typically known to focus on upland plantings for soil and groundwater cleanup, phytotechnology includes all plant-based pollution-remediation and prevention systems, including constructed wetlands, bioswales, green roofs, green walls and planted landfill caps. Taking an even broader view, parks, community gardens and greenways often have phytotechnology components designed into these landscapes, such as protective riparian buffers and vegetated filter strips, where introduced vegetation addresses a range of environmental constraints and pollution control.

Phytotechnologies are based on ecological principles and consider the natural systems as an integral component of human and societal interventions. It is this that makes the use of phytotechnologies integral with evolving landscape architectural design practices. For the remainder of the book the term phytotechnology will be used to describe the comprehensive application of plants on contaminated land and its relationship to the field of landscape architecture and site design.

III	Why do we need phytotechnologies?

Recently ‘greenfield development’ or building on formerly undeveloped or agricultural land has tended to overshadow the reclamation, regeneration and reuse of polluted brownfields. In particular, sites that by virtue of past industrial uses are today contaminated, environmentally disturbed, ecologically threadbare and perceived as economically and socially dysfunctional need remediation to become habitable again.

A The brownfield problem and the need for cost-effective solutions

The class of site known as ‘brownfield’ is universal and gaining more attention. The term is not only found across every part of the country, but in almost every nation and across each continent. The sites are often the most contentious type, politically, ecologically, culturally, economically and aesthetically. They include those with leaking or obsolete underground oil storage tanks, such as gas stations, former industrial sites and former manufactured-gas plants. They also include landfills in varying stages of use from active to closure, railroad corridors, burial grounds and Department of Defense (DOD) military lands. Twenty percent of all real estate transfers in the United States are brownfield sites (Sattler et al., 2010), with the current value of these lands in 2010 in the range of US$2 trillion. The US Environmental Protection Agency (US EPA) estimates there are approximately 450,000–600,000 identified sites located across the country, although this number has been considered unrealistically low (US Accounting Office, 1992). More than 16% of global land areas, equivalent to about 52 million hectares, are impacted by soil pollution worldwide (Anjum, 2013). All these sites, whether large or small, nationally or internationally, need a wider range of cost-effective solutions to clean up or mitigate the risks from soils, groundwater, sediments and existing infrastructure of canals, pools, lagoons and buildings found there.

Remediation technologies are, however, very costly, preventing cleanup of contaminated brownfield sites. The majority of traditional remediation approaches are expensive and energy intensive in their approach to quickly correcting an environmental problem that was decades in the making. Among the remediation methods that are under review by regulatory agencies are phytotechnologies, used either singly or in combination with other industry methods such as removing or capping of polluted soils, and mechanical pumping and treatment of groundwater plumes. The cost-effectiveness of phytotechnologies versus traditional remediation-industry approaches is often a significant advantage and the long-term energy required is often less, since phytotechnologies typically do not require mechanical pumping systems, utility power or much supporting infrastructure and equipment. Plant-based cleanup methods can be as little as 3% of the cost of traditional cleanup costs. Examples provided by author David Glass in his reports (Glass, 1999) demonstrate that phytotechnologies are significantly cheaper than the remediation-industry standard methods. For example, pump-and-treat for groundwater, or incineration of polluted soils, are cheaper by a factor of up to one to thirty; and more specialized methods such as thermal desorption, by a factor of one to ten; soil washing, by a factor of one to four; and bioremediation, by a factor of one to two. These figures, however, do not take into account differences based on individual existing site conditions, location and externalities caused by pollutant types and intensity, climate and human factors, such as the needs for ongoing monitoring, maintenance and site security.

The above-mentioned extent of contaminated sites is based on those already discovered, inventoried and being addressed in some fashion in either the short or long term. There still remains the larger number of landscapes and sites that are in private ownership and currently occupied by industry and manufacturing and that can still produce site pollutants or will be occupied in the future with all the potential for further site contamination. The scale of industrial activities and the number of individual sites may be never ending, with attendant levels of pollution. The potential for plant-based remediation to contribute to the larger cleanup work will increasingly include the design professional, by providing a new set of tools for site regeneration and a source of continual new project work.

B The limitations of conventional remediation practice

Conventional industry remediation practices, such as the ‘pump-and-treat’ (cleaning polluted groundwater through extraction, filtration and recharge methods) and ‘dig-and-haul’ (where polluted soils, as the name suggests, are dug up and shipped off site), are not only expensive but are singleoutcome technologies and have limited site-design potential beyond treatment. Additionally, these traditional remediation approaches are often extremely invasive and disruptive and, by destroying the microenvironment, even leave the soil infertile and unsuitable for agricultural and horticultural uses.

C The build-up of everyday pollutants

The pollution potential of ubiquitous everyday landscapes and installations such as roadways, septic systems and lawn-care applications has recently come to the forefront as a concern. The build-up of contaminants not only affects the surrounding natural resources of an area but also puts a major strain on the local and, in some cases, regional ecosystems. This is due either to prior ignorance of the persistent effects of contamination in the environment, by lack of long-term vision, or to carelessness on the part of local and municipal governments in first legislating for and then administering the overview of environmental regulations. There is a critical need to prevent daily releases of small amounts of pollutants from these widespread land uses.

IV	Opportunities and constraints

In phytotechnology the natural properties and mechanisms of living plants are used to accomplish defined environmental outcomes, especially the reduction of chemicals in soils and groundwater. The diversity of available plants also gives versatility to the application of phytotechnology across a range of landscape locations and types. However, many site conditions and pollution situations render phytotechnologies ‘not viable’ for implementation. A review of the opportunities and constraints for using these technologies is provided below.

A Opportunities

The advantages of the application of phytotechnologies are as follows.

• Plant-based systems are natural, passive, solar energy-driven methods of addressing the cleanup and regeneration of several types of pollution-impacted landscapes.

• The process leaves the soil intact, even improved, unlike other, more invasive methods of site remediation used by the industry, such as removal and disposal, soil washing and thermal desorption.

• Phytotechnologies have the potential to treat a wide range of organic contaminants in the soil and groundwater in low to moderately contaminated sites. However, there are also many cases where phytotechnologies are not applicable. Very specific plant and soil interactions must be considered and monitored for their effectiveness, as detailed in Chapters 2 and 3.

• The use of phytotechnology in a variety of landscape-restoration and environmental installations is attractive to scientists, engineers and designers. These include hybrid technologies combining chemical, physical and other biological processes with plant-based methods.

• Vegetation-based remediation, when applicable, has been found to be less expensive in comparison with other, more conventional, industry-based technologies and approaches.

• Public acceptance is considered high, particularly if the site is located close to or within residential neighborhoods, as phytotechnology is a natural, low-energy, visually and aesthetically pleasing remediation technology.

• The applica...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgements
• Contributors
• Preface
• Foreword by Steven Rock
• List of icons
• List of abbreviations
• 1: Phytotechnology and the contemporary environment: an overview
• 2: Fundamentals
• 3: Contaminant classifications and plant selection
• 4: Phytotypologies: phytotechnology planting types
• 5: Site programs and land use
• 6: Additional resources
• Afterword by Dr. Lee Newman and Dr. Jason White
• Glossary
• Bibliography
• Index